Blends of a polyphenylene ether resin and alkenyl aromatic resins modified with EPDM rubber

ABSTRACT

Novel compositions are disclosed which include a polyphenylene ether resin and an alkenyl aromatic resin modified with an EPDM rubber. Also included with the scope of this invention are reinforced and flame-retardant compositions of said polyphenylene ether resin and said alkenyl aromatic resin modified with an EPDM rubber.

This invention relates to compositions of a polyphenylene ether resinand an alkenyl aromatic resin that is modified with an EPDM rubber.Reinforced and flame-retardant blends are also provided.

BACKGROUND OF THE INVENTION

The term "polyphenylene ether resin" includes a family of polymers wellknown to those skilled in the art, and they are made by a variety ofcatalytic and non-catalytic processes from the corresponding phenols orreactive derivatives thereof. By way of illustration, certain of thepolyphenylene ethers are disclosed in Hay, U.S. Pat. No. 3,306,874 and3,306,875, and in Stamatoff, U.S. Pat. No. 3,257,357 and U.S. Pat. No.3,257,358. In the Hay patents, the polyphenylene ethers are prepared byan oxidative coupling reaction comprising passing an oxygen-containinggas through a reaction solution of a phenol and a metal-amine complexcatalyst. Other disclosures relating to processes using metal-aminecatalyst are found in Bussink et al, U.S. Pat. No. 3,337,499; Blanchardet al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat No. 3,342,892;Borman, U.S. Pat. No. 3,344,166; Hori et al, U.S. Pat. No. 3,384,619;Faurote et al, U.S. Pat. No. 3,440,217; and disclosures relating tometal based catalysts which do not include amines, are known frompatents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines);Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or-phenolate); Kobayashi et al, U.S. Pat. No. 3,455,880 (cobalt chelates);and the like. In the Stamatoff patents, the polyphenylene ethers areproduced by reacting the corresponding phenolate ion with an initiator,such as peroxy acid salt, an acid peroxide, a hypohalite, and the like,in the presence of a complexing agent. Disclosures relating tonon-catalytic processes, such as oxidation with lead dioxide, silveroxide, etc. are described in Price et al, U.S. Pat. No. 3,382,212. Allof the above-mentioned disclosures are incorporated herein by reference.

The term "alkenyl aromatic resin" includes polymers and copolymers ofstyrene, alpha methyl styrene, chlorostyrene, ethylvinylbenzene,divinylbenzene, vinylnaphthalene and the like.

The term "EPDM" includes rubbery interpolymers of a mixture ofmono-olefins and a polyene. Preferred type are those rubberyinterpolymers of ethylene, an alpha-olefin and a polyene.

In the prior art rubber-modified styrene resins have been admixed withpolyphenylene ether resins to form compositions that have modifiedproperties. The Cizek patent, U.S. Pat. No. 3,383,435 disclosesrubber-modified styrene resin-polyphenylene ether resin compositionwherein the rubber component is of the unsaturated type such as polymersand copolymers of butadiene. The physical properties of thesecompositions are such that it appears that many of the properties of thestyrene resins have been upgraded, while the moldability of thepolyphenylene ethers are improved.

Ger. Offen. No. 2,047,613 discloses that less than 30 by weight of anEPDM modified styrene resin may be used to upgrade the impact strengthof polyphenylene ether resins. There is no suggestion to use higheramounts or that higher amounts will improve the oxidative stability andcolor stability of a polyphenylene ether composition.

It has now been found that when the highly unsaturated rubber that isused in compositions of the type disclosed by Cizek, is replaced withEPDM rubber that has a low degree of residual unsaturation, the thermaloxidative stability and color stability are improved.

It is, therefore, a primary object of this invention to provide improvedcompositions of polyphenylene ether resins and modified alkenyl aromaticresins.

Another object of this invention is to provide molding compositions andmolded articles of a polyphenylene ether resin and a modified alkenylaromatic resin which have improved thermal oxidative stability.

Still another object of this invention is to provide moldingcompositions and molded articles of a polyphenylene ether resin and amodified alkenyl aromatic resin which have improved color stability.

It is also an object of this invention to provide the above-described,improved molding compositions in particular embodiment that arereinforced and/or flame retardant.

DESCRIPTION OF THE INVENTION

The above-mentioned advantages and objects and others will be readilyapparent to those skilled in the art by the following compositions.

Preferred types will include thermoplastic compositions which comprise:

a. from 20-65% by weight of a polyphenylene ether resin and

b. from 35-80% by weight of an alkenyl aromatic resin that is modifiedwith an EPDM rubber, that is, a rubbery interpolymer of a mixture ofmono-olefins and a polyene. These rubbery interpolymers include thoseprepared from ethylene, an alpha-olefin and a polyene. Preferred typescomprise 10-90 mole percent of ethylene, 10-90 mole percent of analpha-olefin containing 3-16 carbon atoms and 0.1-10 mole percent of apolyene that is a non-conjugated cyclic or open-chain diene that hasfrom 4-20 carbon atoms. Especially preferred are those alpha-olefinshaving 3-10 carbon atoms and non-conjugated cyclic or open-chain dienehaving from 5-10 carbon atoms.

The alkenyl aromatic resins are well known and are derived from monomersof the formula: ##SPC1##

wherein R¹ and R² are selected from the group consisting of lower alkylor alkenyl groups of from 1 to 6 carbon atoms and hydrogen; R³ and R⁴are selected from the group consisting of chloro, bromo, hydrogen andlower alkyl of from 1 to 6 carbon atoms; R⁵ and R⁶ are selected from thegroup consisting of hydrogen and lower alkyl and alkenyl groups of from1 to 6 carbon atoms or R⁵ and R⁶ may be concatenated together withhydrocarbyl groups to form a naphthyl group. These compounds are free ofany substituent that has a tertiary carbon atom.

Specific examples of alkenyl aromatic monomers include styrene,chlorostyrene, alpha-methylstyrene, vinyl xylene, divinylbenzene andvinyl naphthalene.

The preferred polyphenylene ethers are of the formula: ##SPC2##

wherein Q is selected from the group consisting of hydrogen, hydrocarbonradicals, halohydrocarbon radicals having at least two carbon atomsbetween the halogen atom and the phenol nucleus, hydrocarbonoxy radicalsand halohydrocarbonoxy radicals having at least two carbon atoms betweenthe halogen atoms and the phenol nucleus, Q' and Q" are the same as Q,and in addition, halogen with the proviso that Q, and Q' are all free ofa tertiary carbon atom; and n is an integer of at least 50.

Especially preferred is poly (2,6-dimethyl-1,4-phenylene) ether.

The alkenyl aromatic resin that is modified with a rubbery interpolymerof a mixture of mono-olefins and a polyene may be prepared by dissolvingthe rubbery interpolymer in the alkenyl aromatic monomer andpolymerizing the mixture in the presence of a free-radical initiatoruntil 90-100% by weight of the alkenyl aromatic monomer has reacted toform said modified alkenyl aromatic resin. These materials arecommercially available, such as the product Taflite 925-01 which is asuspension polymerized EPDM modified, high-impact polystyrene thatcontains about 12% of benzene insoluble rubber and the average rubberparticle size is about 8-10 microns. The EPDM component appears to be anethylene-propylene-ethylidene norbornene terpolymer. They are alsodescribed in U.S. Pat. No. 3,538,192, which is hereby incorporated byreference. Also, the EPDM rubbers are described in: Vinyl and AlliedPolymer, P. D. Ritchie, Volume 1, Page 121 (1968) and the EPDM modifiedresins are described in: J. Appl. Polymer Sci., Volume 16, Pages1125-1138 (1972) which are also incorporated by reference. The preferredmodified alkenyl aromatic resins are those made with an EPDM rubberyinterpolymer of ethylene, propylene and 5-ethylidene-2-norbornene andstyrene. Preferred modified alkenyl aromatic resins will include fromabout 5 to about 20% by weight of rubbery interpolymer.

As reinforcing fillers, there may be employed reinforcing amounts ofreinforcing filler. In general, any reinforcement can be used, e.g.,aluminum, iron or nickel, and the like, and non-metals, e.g., carbonfilaments, silicates, such as acicular calcium silicate, asbestos, TiO₂,potassium titanate and titanate whiskers, glass flakes and fibers andthe like. It is to be understood that, unless the filler adds to thestrength and stiffness of the composition, it is only a filler and not areinforcing filler as contemplated herein. In particular, thereinforcing fillers increase the flexural strength, the flexuralmodulus, the tensile strength and the heat distortion temperature.

Although it is only necessary to have at least a reinforcing amount ofthe reinforcement present, in general, the combination of components (a)and (b) will comprise from about 10 to about 90 parts by weight and thefiller will comprise from about 10 to about 90 parts by weight of thetotal composition.

In particular, the preferred reinforcing fillers are of glass and it ispreferred to use fibrous glass filaments comprised of lime-aluminumborosilicate glass that is relatively soda free. This is known as "E"glass. However, other glasses are useful where electrical properties arenot so important, e.g., the low soda glass known as "C" glass. Thefilaments are made by standard processes, e.g., by steam or air blowing,flame blowing and mechanical pulling. The preferred filaments forplastics reinforcement are made by mechanical pulling. The filamentdiameters range from about 0.000112 to 0.00075 inch, but this is notcritical to the present invention.

In general, best properties will be obtained if the sized filamentousglass reinforcement comprises from about 1 to about 80% by weight basedon the combined weight of glass and polymers and preferably from about10 to about 50% by weight. Especially preferably the glass will comprisefrom about 10 to about 40% by weight based on the combined weight ofglass and resin. Generally, for direct molding use, up to about 60% ofglass can be present without causing flow problems. However, is ituseful also to prepare the compositions containing substantially greaterquantities, e.g., up to 70-80% by weight of glass. These concentratescan then be custom blended with blends of resins that are not glassreinforced to provide any desired glass content of a lower value.

The length of the glass filaments and whether or not they are bundledinto fibers and the fibers bundled in turn to yarns, ropes or rovings,or woven into mats, and the like, are also not critical to theinvention. However, in preparing the present compositions it isconvenient to use the filamentous glass in the form of chopped strandsof from about 1/8 in. to about 1 inch long, preferably less than 1/4 in.long. In articles molded from the compositions, on the other hand, evenshorter lengths will be encountered because, during compounding,considerable fragmentation will occur. This is desirable, however,because the best properties are exhibited by thermoplastic injectionmolded articles in which the filament lengths lie between about 0.000005in. and 0.125 (1/8 inch).

Because it has been found that certain commonly used flammable sizingson the glass, e.g., dextrinized starch or synthetic polymers, contributeflammability often in greater proportion than expected from the amountpresent, it is preferred to use lightly sized or unsized glassreinforcements in those compositions of the present invention which areflame retardant. Sizings, if present, can readily be removed by heatcleaning or other techniques well known to those skilled in the art.

It is a preferred feature of this invention also to provide flameretardant thermoplastic compositions, as defined above by modifying thecomposition to include a flame-retardant additive in a minor proportionbut in an amount at least sufficient to render the compositionnon-burning or self-extinguishing.

A preferred feature of the invention is a flame-retardant composition asabove defined, which also includes a halogenated organic compound, ahalogenated organic compound in admixture with an antimony compound,elemental phosphorus or a phosphorus compound or compounds containingphosphorus-nitrogen bonds or a mixture of two or more of the foregoing.

When used herein, the terms "non-burning", "self-extinguishing" and"non-dripping" are used to describe compositions which meet thestandards of ASTM test method D-635 and Underwriters' LaboratoriesBulletin No. 94. Another recognized procedure to determine flameresistance of resinous compositions is the Oxygen Index Test or LOI(Limiting Oxygen Index). This test is a direct measure of a product'scombustibility based on the oxygen content of the combustion atmosphere.Appropriate specimens are placed in a combustion chimney and the oxygenis reduced stepwise until the material no longer supports a flame. TheLOI is defined as the precent oxygen times 100 divided by the sum of thepercentages of nitrogen and oxygen in the gas used to burn the materialunder test. Further details of the Oxygen Index Test are found in ASTMtest Method D-2863. The compositions of this invention which containflame-retardant additives in the specified amounts have a substantiallyhigher oxygen index and thus are much less combustible than thecontrols.

The flame-retardant additives useful in this invention comprise a familyof chemical compounds well known to those skilled in the art. Generallyspeaking, the more important of these compounds contain chemicalelements employed for their ability to impart flame resistance, e.g.,bromine, chlorine, antimony, phosphorus and nitrogen. It is preferredthat the flame-retardant additive comprise a halogenated organiccompound (brominated or chlorinated); a halogen-containing organiccompound in admixture with antimony oxide; elemental phosphorus or aphosphorus compound; a halogen-containing compound in admixture with aphosphorus compound or compounds containing phosphorus-nitrogen bonds ora mixture of two or more of the foregoing.

The amount of flame-retardant additive used is not critical to theinvention, so long as it is present in a minor proportion based on saidcomposition--major proportions will detract from physical properties --but at least sufficient to render the polyphenylene ether-modifiedalkenyl aromatic polymer blend non-burning or self-extinguishing. Thoseskilled in the art are well aware that the amount will vary with thenature of the polymers in the blend and with the efficiency of theadditive. In general, however, the amount of additive will be from 0.5to 50 parts by weight per hundred parts of components (a) plus (b). Apreferred range will be from about 3 to 25 parts and an especiallypreferred range will be from about 5 to 15 parts of additive per 100parts of (a) plus (b). Smaller amounts of compounds highly concentratedin the elements responsible for flame-retardance will be sufficient,e.g., elemental red phosphorus will be preferred at 0.5 to 10 parts byweight per hundred parts of (a) plus (b), while phosphorus in the formof triphenyl phosphate will be used at 5 to 25 parts of phosphate perpart of (a) plus (b), and so forth. Halogenated aromatics will be usedat 2 to 20 parts and synergists, e.g., antimony oxide, will be used atabout 1 to 10 parts by weight per 100 parts of components (a) plus (b).

Among the useful halogen-containing compounds are those of the formula##SPC3##

wherein n is 1 to 10 and R is an alkylene, alkylidene or cycloaliphaticlinkage, e.g., methylene, ethylene, propylene, isopropylene,isopropylidene, butylene, isobutylene, amylene, cyclohexylene,cyclopentylidene, and the like; a linkage selected from the groupconsisting of ether; carbonyl; amine; a sulfur-containing linkage, e.g.,sulfide, sulfoxide, sulfone, carbonate; a phosphorus-containing linkage;and the like. R can also consist of two or more alkylene or alkylidenelinkages connected by such groups as aromatic, amino, ether, ester,carbonyl, sulfide, sulfoxide, sulfone, a phosphorus-containing linkage,and the like. R can be a dihydric phenol, e.g., bisphenol-A, carbonatelinkage. Other groups which are represented by R will occur to thoseskilled in the art. Compounds of this type are disclosed in U.S. Pat.No. 3,647,747 and U.S. Pat. No. 3,334,154 both of which are incorporatedby reference.

Ar and Ar' are mono- or polycarbocyclic aromatic groups such asphenylene, biphenylene, terphenylene, naphthylene, and the like. Ar andAr' may be the same or different.

Y is a substituent selected from the group consisting of organic,inorganic or organometallic radicals. The substituents represented by Yinclude (1) halogen, e.g., chlorine, bromine, iodine, or fluorine or (2)ether groups of the general formula OE, wherein E is a monovalenthydrocarbon radical similar to X or (3) monovalent hydrocarbon groups ofthe type represented by R or (4) other substituents, e.g., nitro, cyano,etc., said substituents being essentially inert provided there be atleast one and preferably two halogen atoms per aryl, e.g., phenyl,nucleus.

X is a monovalent hydrocarbon group exemplified by the following: alkyl,such as methyl, ethyl, propyl, isopropyl, butyl, decyl, and the like;aryl groups, such as phenyl, naphthyl, biphenyl, xylyl, tolyl, and thelike; aralkyl groups, such as benzyl, ethylphenyl, and the like;cycloaliphatic groups, such as cyclopentyl, cyclohexyl, and the like; aswell as monovalent hydrocarbon groups containing inert substituentstherein. It will be understood that where more than one X is used theymay be alike or different.

The letter d represents a whole number ranging from 1 to a maximumequivalent to the number of replaceable hydrogens substituted on thearomatic rings comprising Ar or AR'. The letter e represents a wholenumber ranging from 0 to a maximum controlled by the number ofreplaceable hydrogens on R. The letters a, b, and c represent wholenumbers including 0. When b is not 0, neither a nor c may be 0.Otherwise, either a or c, but not both, may be 0. Where b is 0, thearomatic groups are joined by a direct carbon-carbon bond.

The hydroxyl and Y substituents on the aromatic groups, Ar and Ar' canve varied in the ortho, meta or para positions on the aromatic rings andthe groups can be in any possible geometric relationship with respect toone another.

Included within the scope of the above formula are di-aromatics of whichthe following are representative:

2,2-bis-(3,5-dichlorophenyl)propane

bis-(2-chlorophenyl)methane

bis-(2,6-dibromophenyl)methane

1,1-bis-(4-iodophenyl)ethane

1,2-bis-(2,6-dichlorophenyl)ethane

1,1-bis-(2-chloro-4-iodophenyl)ethane

1,1-bis-(2-chloro-4-methylphenyl)ethane

1,1-bis-(3,5-dichlorophenyl)ethane

2,2-bis-(3-phenyl-4-bromophenyl)ethane

2,3-bis-(4,6-dichloronaphthyl)propane

2,2-bis-(2,6-dichlorophenyl)pentane

2,2-bis-(3,5-dichromophenyl)hexane

bis-(4-chlorophenyl)phenylmethane

bis-(3,5-dichlorophenyl)cyclohexylmethane

bis-(3-nitro-4-bromophenyl)methane

bis-(4-hydroxy-2,6-dichloro-3-methoxyphenyl)methane

2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane

2,2-bis-(3-bromo-4-hydroxyphenyl)propane

The preparation of these and other applicable biphenyls are known in theart. In place of the divalent aliphatic group in the above examples maybe substituted sulfide, sulfoxy, and the like.

Included within the above structural formula are substituted benzenesexemplified by tetrabromobenzene, hexachlorobenzene, hexabromobenzene,and biphenyls such as 2,2'-dichlorobiphenyl, 2,4'-dibromobiphenyl,2,4'-dichlorobiphenyl, hexabromobiphenyl, octabromobiphenyl,decabromobiphenyl and halogenated diphenyl ethers, containing 2 to 10halogen atoms.

The preferred halogen compounds for this invention are aromatic halogencompounds such as chlorinated benzene, brominated benzene, chlorinatedbiphenyl, chlorinated terphenyl, brominated biphenyl, brominatedterphenyl or a compound comprising two phenyl radicals separated by adivalent alkylene group and having at least two chlorine or bromineatoms per phenyl nucleus, and mixtures of at least two of the foregoing.

Especially preferred are hexabromobenzene and chlorinated biphenyls orterphenyls, alone, or mixed with antimony oxide.

In general, the preferred phosphate compounds are selected fromelemental phosphorus or organic phosphonic acids, phosphonates,phosphinates, phosphonites, phosphinites, phosphene oxides, phosphenes,phosphites or phosphates. Illustrative is triphenyl phosphine oxide.These can be used alone or mixed with hexabromobenzene or a chlorinatedbiphenyl and, optionally, antimony oxide.

Typical of the preferred phosphorus compounds to be employed in thisinvention would be those having the general formula ##EQU1## andnitrogen analogs thereof where each Q represents the same or differentradicals including hydrocarbon radicals such as alkyl, cycloalkyl, aryl,alkyl substituted aryl and aryl substituted alkyl; halogen; hydrogen andcombinations thereof provided that at least one of said Q's is aryl.Typical examples of suitable phosphates include, phenylbisdodecylphosphate, phenylbisneopentyl phosphate, phenylethylene hydrogenphosphate, phenyl-bis-(3,5,5'-trimethylhexyl phosphate), ethyldiphenylphosphate, 2-ethylhexyl di(p-tolyl) phosphate, diphenyl hydrogenphosphate, bis(2-ethylhexyl) p-tolylphosphate, tritolyl phosphate,bis(2-ethylhexyl)-phenyl phosphate, tri(nonylphenyl) phosphate,phenylmethyl hydrogen phosphate, di(dodecyl) p-tolyl phosphate,tricresyl phosphate, triphenyl phosphate, halogenated triphenylphosphate, dibutylphenyl phosphate, 2-chloroethyldiphenyl phosphate,p-tolyl bis(2,5,5'-trimethylhexyl) phosphate, 2-ethylhexyldiphenylphosphate, diphenyl hydrogen phosphate, and the like. The preferredphosphates are those where each Q is aryl. The most preferred phosphateis triphenyl phosphate. It is also preferred to use triphenyl phosphatein combination with hexabromobenzene and, optionally, antimony oxide.

Also suitable as flame-retardant additives for this invention arecompounds containing phosphorus-nitrogen bonds, such as phosphonitrilicchloride, phosphorus ester amides, phosphoric acid amides, phosphonicacid amides, phosphinic acid amides, tris)aziridinyl)phosphine oxide ortetrakis (hydroxymethyl) phosphonium chloride. These flame-retardantadditives are commercially available.

The blends may be formed by conventional techniques, that is by firstdry mixing the components and, thereafter, melt blending the compositionin an extruder.

By way of illustration, glass roving (a bundle of strands of filaments)is chopped into small pieces, e.g., 1/8 in. to 1 inch in length, andpreferably less than 1/4 inch in length and put into an extrusioncompounder with (a) the polyphenylene ether resin, (b) the alkenylaromatic resin that is modified with a rubbery interpolymer of a mixtureof monoolefins and a polyene, the flame-retardant additive(s) and (e) toproduce molding pellets. The fibers are shortened and predispersed inthe process, coming out at less than 1/16 inch long. In anotherprocedure, glass filaments are ground or milled to short lengths, andare mixed with the polyphenylene ether resin, the modified alkenylaromatic polymer and, optionally, flame retardant additive by dryblending then either fluxed on a mill and ground, or they are extrudedand chopped.

In addition, compounding should be carried out to insure that theresidence time in the machine is short; the temperature is carefullycontrolled; the frictional heat is utilized; and an intimate blendbetween the resins and the additives is obtained. Various pigments,fillers and processing aids may also be used according to techniqueswell known to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples are set forth as further descriptions of theinvention, but are not to be construed as limiting the inventionthereto.

EXAMPLE I

A blend having the following composition was prepared:

                             Grams                                                ______________________________________                                        poly(2,6-dimethyl-1,4-phenylene)ether                                         (PPO, General Electric Company having                                         a intrinsic viscosity of about 0.52                                           deciliters/gram measured in chloro-                                           form at 30°C).      35                                                 polystyrene modified with a terpolymer                                        of ethylene, propylene and 5-ethylidene-                                      2-norbornene having a Mooney viscosity of                                     140 (ML-8) (prepared according to Example                                     VIII of U.S. 3,538,192).   65                                                 ______________________________________                                    

This blend is prepared with a twin screw extruder at 585°F and theextruded pellets were molded into standard test pieces with a Newburyinjection molding machine, barrel temperature 450°F.

EXAMPLE II

A blend having the following composition was prepared:

                            Gram                                                  ______________________________________                                        poly(2,6-dimethyl-1,4-phenylene)                                              ether (PPO, General Electric Com-                                             pany, having an intrinsic viscosity                                           of about 0.52 deciliters/gram when                                            measured in chloroform at 30°C.)                                                                 700.0                                               polystyrene resin modified with a                                             rubbery interpolymer of a mixture                                             of monoolefins and a polyene                                                  (Taflite 925-01, Mitsui Toatsu                                                Chemical Co.).            1300.0                                              triphenyl phosphate       140.0                                               tridecyl phosphite        10.0                                                polyethylene                                                                  (Microthene M-710)        30.0                                                titanium dioxide          100.0                                               ______________________________________                                    

The blend was prepared with a twin-screw extruder at 585°F and theextruded pellets were molded into standard test pieces such as tensilebars with a Newbury injection molding machine, barrel temperature 450°F.

EXAMPLE III

The following composition was prepared according to the procedure setforth in Example II:

                            Grams                                                 ______________________________________                                        poly(2,6-methyl-1,4-phenylene)                                                ether (as used in Example II)                                                                           1000.0                                              polystyrene resin modified with                                               a rubbery interpolymer of a                                                   mixture of monoolefins and a poly-                                            ene (as used in Example II)                                                                             1000.0                                              triphenyl phosphate       60.0                                                tridecylphosphate         10.0                                                zinc sulfide              3.0                                                 zinc oxide                3.0                                                 polyethylene                                                                  (Microthene M-710)        30.0                                                titanium dioxide          100.0                                               ______________________________________                                    

CONTROL SPECIMENS

A first control specimen was prepared according to the method of ExampleII except that a polybutadiene modified, high-impact polystyrene (FosterGrant 834) was substituted for the polystyrene that was modified with arubbery interpolymer of a mixture of monoolefins and a polyene.

A second control specimen was prepared according to the method ofExample III except that a polybutadiene modified, high-impactpolystyrene (Foster Grant 834) was substituted for the polystyrene thatwas modified with a rubber interpolymer of a mixture of monoolefins anda polyene.

A test specimen prepared in Example II and the first control specimenwere heat aged in an air oven at 105°C after initial physical propertieswere measured. At periodic intervals the specimens were removed andtested on an Instron machine at a speed of one inch per minute. Thetensile bars of Example III and the second control specimen wereprocessed similarly except that the oven temperature was 115°C. Theresults were as follows:

                                      TABLE I                                     __________________________________________________________________________    Specimen Alkenyl Resin                                                                            Wt. Ratio                                                                            HDT TS  Elongation                                                                          Time to Embrittlement                                    (PPO:AR)                                                                             (°F)                                                                       (psi)                                                                             (%)   Days at 105°C                                                                   Days at                     __________________________________________________________________________                                                      115°C                Example II                                                                             rubbery interpo-                                                              lymer modified                                                                polystyrene                                                                              35:65  202 7000                                                                              36    100      --                          First Control                                                                          polybutadiene modi-                                                           fied polystyrene                                                                         35:65  208 7200                                                                              73     20      --                          Example III                                                                            rubbery interpo-                                                              lymer modified                                                                polystyrene                                                                              50:50  250 8300                                                                              22    --        90-100                     Second Control                                                                         polybutadiene modi-                                                           fied polystyrene                                                                         50:50  252 8500                                                                              58    --       25-28                       __________________________________________________________________________

It can be seen that the compositions of this invention at the 50:50level of Example III show a four-fold increase in the time toembrittlement as compared to the prior art control specimen. Theimprovement was even greater for the 35:65 blends. The test barsaccording to this invention also showed much less darkening on exposureto heat-aging than did the prior control specimens.

EXAMPLE IV BLEND A

A blend of the following composition was prepared by extrusion on a W-Ptwin-screw extruder:

                           Grams                                                  ______________________________________                                        poly(2,6-dimethyl-1,4-phenylene)                                              ether (as used in Example I)                                                                           250.0                                                polystyrene modified with a                                                   rubbery interpolymer of a                                                     mixture of monoolefins and a                                                  polyene (as used in Example II)                                                                        250.0                                                polyethylene (Microthene M-710)                                                                        7.5                                                  triphenyl phosphate      15.0                                                 tridecyl phosphite       2.5                                                  zinc sulfide             0.75                                                 zinc oxide               0.75                                                 ______________________________________                                    

Standard test pieces were molded from the chopped extrudate in a Newburyinjection molding machine. Three additional blends of the samecomposition were prepared using the same technique except that areinforcement was incorporated prior to extrusion:

    BLEND B 8% (by wt.) of glass fibers (497 BB chopped                                   glass fibers). Owens Corning Fiberglass Corp.                         BLEND C 16% (by wt.) of acicular calcium silicate                                     (Wallastonite F-1, Interpace Corp.).                                  BLEND D 16% (by wt.) of potassium titanate                                            (Fybex, Dupont).                                                  

The blends were tested and the following results were noted:

                  TABLE II                                                        ______________________________________                                        Blend Filler     Tensile  Flexural                                                                             Flexural                                                                              HDT                                                   Strength Strength                                                                             Modulus                                      ______________________________________                                                         (psi)    (psi)          (°C)                          A     none       7600     12,300 472,000 113                                  B     8% glass   12,300   17,700 644,000 120                                  C     16% cal-                                                                      cium sili-                                                                    cate       10,600   15,600 618,000 120                                  D     16% potas-                                                                    sium tita-                                                                    nate       13,800   20,000 850,000 122                                  ______________________________________                                    

It can readily be seen that the reinforced blend compositions accordingto this invention have enhanced physical properties.

EXAMPLE V

A blend was prepared having the following composition:

    BLEND E                                                                                                Grams                                                ______________________________________                                        poly (2,6-dimethyl-1,4-phenylene)                                             ether (as used in Example I)                                                                           250.0                                                polystyrene resin modified with                                               a rubber interpolymer of mono-                                                olefins and a polyene (as used                                                in Example II)           250.0                                                polyethylene (Microthene M-710)                                                                        7.5                                                  titanium dioxide         25.0                                                 ______________________________________                                    

The blend was prepared according to the technique of Example III andstandard flame bars, 1/16 inch thick were molded on a Newbury injectionmolding machine.

By the same technique, the following blends were prepared with therecited flame retardants added to the blend having the same compositionas Blend E.

    ______________________________________                                                  Flame retardant                                                     ______________________________________                                        BLEND F    triphenylphosphate (3 phr)                                         BLEND G    triphenylphosphate (5 phr)                                         BLEND H    3,3',5,5' tetramethyl-2,2',6,6'-                                              tetrabromo-4,4'-dihydroxybiphenyl                                             (5 phr) and Sb.sub.2 O.sub.3 (2 phr)                               BLEND I    copolymer of bisphenol A and tetra-                                           bromobisphenol A containing about                                             21% bromine (prepared according to                                            Example I of U.S. 3,647,747)                                                  (8.5 phr) and Sb.sub.2 O.sub.3 (1 phr)                             BLEND J    hexabromobiphenyl (3 phr) and                                                 Sb.sub.2 O.sub.3 (1 phr)                                           ______________________________________                                    

Test bars (1/16 inch thick) prepared from Blends E-J were testedaccording to the procedure of UL subject 94. The results are listed inTable III:

                  TABLE III                                                       ______________________________________                                        Blend     Average Burning Time (a)                                                                          Remarks                                         ______________________________________                                                  (seconds)                                                           E         57 (b)              Drip                                            F         27                                                                  G         16                  SE-1                                            H         23                                                                  I         24                                                                  J         21                                                                  ______________________________________                                         (a) Average of 10 ignitions; 5 bars, each ignited twice.                      (b) First ignition only; dripping prevented reignition.                  

Obviously, other modifications and variations of the present inventionare possible in the light of the above teachings. It is, therefore, tobe understood that changes may be made in the particular embodiments ofthe invention described which are within the full intended scope of theinvention as defined by the appended claims.

We claim:
 1. A thermoplastic molding composition which comprises:a. from 20-65% by weight of a polyphenylene ether resin and b. from 35-80% by weight of an alkenyl aromatic resin that is modified with a rubbery interpolymer of a mixture of monoolefins and a polyene by polymerizing an alkenyl aromatic monomer in the presence of said rubbery interpolymer.
 2. The molding composition of claim 1 wherein the modifier is a rubbery interpolymer of ethylene, an alpha-olefin and a polyene.
 3. The molding composition of claim 1 wherein said rubbery interpolymer comprises 10-90 mole percent of ethylene, 10-90 mole percent of an alpha-olefin containing 3-16 carbon atoms and 0.1-10 mole percent of a polyene that is a non-conjugated cyclic or open-chain diene that has from 4-20 carbon atoms.
 4. The molding composition of claim 3 wherein the polyphenylene ether resin is selected from compounds of the formula: ##SPC4##wherein Q is selected from the group consisting of hydrogen, hydrocarbon radicals, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenol nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atoms and the phenol nucleus, Q' and Q" are the same as Q, and in addition, halogen with the proviso that Q and Q' are all free of a tertiary carbon atom; and n is an integer of at least
 50. 5. The molding composition of claim 3 wherein the alkenyl aromatic resin is selected from the group consisting of styrene, alpha-methylstyrene, vinyl xylene, chlorostyrene, divinylbenzene and vinyl naphthalene.
 6. A thermoplastic molding composition which comprises:a. from 20-65% by weight of a polyphenylene ether resin and b. from 35-80% by weight of an alkenyl aromatic resin that is modified with a rubbery interpolymer which comprises 10-90 mole percent of ethylene, 10-90 mole percent of an alpha olefin having from 3-10 carbon atoms and from 0.1-10 mole percent of a polyene that is a non-conjugated cyclic or open-chain diene that has from 5-10 carbon atoms by polymerizing an alkenyl aromatic monomer in the presence of said rubbery interpolymer.
 7. The molding composition of claim 6 wherein said polyphenylene ether resin is poly(2,6-dimethyl-1,4-phenylene) ether.
 8. The molding composition of claim 6 wherein said alkenyl aromatic resin is styrene and said rubbery interpolymer is present at a ratio between 1:4 and 4:1 by weight of styrene to rubbery interpolymer.
 9. The molding composition of claim 8 wherein said rubbery interpolymer comprises 10-90 mole percent of ethylene 10-90 mole percent of propylene and 0.1-10 mole percent of 5-ethylidene-2-norbornene. 